I consider my Twitter account to be a great source of information and professional learning. Many educators and librarians twitter and I follow them to keep up with trends in education. Generally Twitter feeds back to blogs where subjects and topics are expanded upon
Science

60 + science blogs selected on the basis of their originality, insight, talent, and dedication provide up-to-date coverage of their different fields

Biology

Chemistry

Physics

Globalisation

• http://fairerglobalization.blogspot.com/
  Globalization and human rights
  Global Health

Information Technology

• http://techcrunch.com/
  Microsoft programming blogs

Mathematics